1. Field of the Invention
This invention relates to a flash-lamp system, and particularly to a flash-lamp string comprising two different types of flash-lamp strings.
2. Description of the Prior Art
In a conventional flash-lamp string usually comprises a separate power-supply wire connected with a plurality of lamp sockets which are connected in series; the last lamp socket on the end of the string is connected with a separate power-supply wire; then, the two separate power-supply wires are twisted together to form into a lamp string; each socket is mounted with a bulb; the lamp string is used as a decoration; every lamp string is mounted with a thermal cut-out bulb so as to have all the rest bulbs turned on and off continuously, i.e., to provide a flash effect. A plurality of lamp strings can be connected in parallel, and twisted into an elongate lamp string; such an elongate lamp string is referred as a regular flash-lamp string.
A conventional flash-lamp string comprises a plurality of lamp sockets connected in series, and some of the lamp sockets are mounted with thermal cut-out bulbs so as to reduce the current flow in the lamp string, and have the rest bulbs had more brightness; in other words, when the thermal cut-out bulbs are turned off, the rest bulbs would provide more brightness because of gaining more current. Since the thermal cut-out bulbs are turned off at different time, the whole lamp string would provide an irregular variation of brightness; in that case, the bulb in the lamp string must have a tungsten filament able to withstand a higher current so as to provide brightness as desired. Such a lamp string is referred to as a Twinkle lamp string; however, such a lamp string should not be connected with too many thermal cut-out bulbs so as to prevent from causing a danger of overheating.
Another conventional flash-lamp string, such as disclosed in U.S. Pat. No. 6,474,841, includes a plurality of different lamp strings in terms of shape and size; in that case, the regular flash bulb and the winkle flash bulb can not be mounted in a non-compatible lamp socket. According to the embodiment of the aforesaid patent, the difference of shape and size can simply indicate the difference of the bulbs, i.e., a different bulb can not be mounted in a non-compatible lamp socket.